This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. 2/27/2008 Hypothesis: Cetirizine (Zyrtec) provides more rapid relief and less sedation compared to Benadryl in the treatment of acute allergic food reactions. Diphenhydramine (Benadryl) has been commonly used as the antihistamine of choice for acute food allergic reactions given its quick onset of action and ready availability. However, sedation is a common side effect of diphenhydramine, which can complicate the assessment of a patient being treated for an acute allergic food reaction. Cetirizine (Zyrtec) is a newer generation antihistamine with a longer duration of action and less sedating side effects. A direct comparison of the onset of action and side effect profile of cetirizine to diphenhydramine has not been made for the treatment of allergic food reactions. If cetirizine offers quick onset of antihistaminic relief with less sedation compared to diphenhydramine, cetirizine would be an attractive alternative to diphenhydramine in the treatment of acute food allergic reactions.